4-chloro-5-nitro-1H-pyrazole-3-carboxylic acid → HCID 178509123, compound

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Reaction Steps

Crude 16 (10.0 g, 52.2 mmol) was heated in water (100 mL) to 60° C. int. temperature. The product intermediate 16 contained manganese salts as an impurity, but could be used unpurified in the Raney-Ni reduction to obtain intermediate 17. To this solution was added Raney-Ni (7 g, 50% slurry in water) and dropwise over 4 hours a solution of hydrazine monohydrate (20 mL) in water (200 mL). Hydrazine was more effective as a hydrogen source in this reduction than hydrogen provided at 1 bar. After 1 hour at 60° C. int. temperature the mixture was allowed to cool to ambient temperature, filtered through celite, the filter cake washed with water (200 mL) and the combined filtrates evaporated and dried in vacuo to afford crude 17 (15 g, max. 52.2 mmol), which contained some Ni salts and was used unpurified in the next step.

Provenance & Evidence